Posted by **BRENDAN** on Tuesday, September 29, 2009 at 12:53am.

Please show the quickest way to do this question?

Amanda has 20 coins in her purse. She has only 10c,20c and 50c coins, and their total value is $5. If she has more 50c than 10c coins, how many 10c has she?

Thank You

- MATHS -
**Dean**, Tuesday, September 29, 2009 at 12:59am
Are you in algebra using variables 'c'?

- MATHS -
**BRENDAN**, Tuesday, September 29, 2009 at 1:13am
I'm not sure what you mean.

- MATHS -
**Dean**, Tuesday, September 29, 2009 at 1:15am
What grade are you in?

- MATHS -
**BRENDAN**, Tuesday, September 29, 2009 at 1:18am
YEAR 4

- MATHS -
**Dean**, Tuesday, September 29, 2009 at 1:21am
c stands for cents?

- MATHS -
**BRENDAN**, Tuesday, September 29, 2009 at 1:27am
yes c stands for cents.

- MATHS -
**Dr Russ**, Tuesday, September 29, 2009 at 4:16am
I got 4 x 50c = $2

2 x 10c = 20 c

14 x 20c = $2.80c

so she has 2 x 10c

- MATHS -
**Reiny**, Tuesday, September 29, 2009 at 8:57am
Since you are in year 4, you will be able to solve this algebraically.

let the number of 10c pieces be x

let the number of 20c pieces be y

let the number of 50c pieces be (20-x-y)

10x + 20y + 50(20-x-y) = 500

reduces to

4x + 3y = 50

so we need positive integer solutions for x and y

clearly x has to be between 0 and 13

after only two tries, I got

x = 2, and y = 14

then

number of 10c pieces = 2

number of 20c pieces = 14

number of 50c pieces = 20-2-14 = 4

check: 2x10 + 14x20 + 4x50 = 500

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